Exercise capacity in patients supported with rotary blood pumps is improved by a spontaneous increase of pump flow at constant pump speed and by a rise in native cardiac output

Exercise capacity is improved in patients supported with continuous flow rotary blood pumps (RP). The aim of this study was to investigate the mechanisms underlying this improvement. Ten patients implanted with a RP underwent cardiopulmonary exercise testing (CPET) at 6 months after surgery with hemodynamic and metabolic measurements (RP group). A group of 10 matched heart failure patients were extracted from our heart transplant database, and the results of their last CPET before transplantation were used for comparison (heart failure [HF] group). Peak VO(2) was significantly higher in RP than in HF patients (15.8 ± 6.2 vs. 10.9 ± 3 mL O(2)/kg.min) reaching 52 ± 16% of their predicted peak VO(2). The total output measured by a Swan-Ganz catheter increased from 5.6 ± 1.6 to 9.2 ± 1.8 L/min in the RP group and was significantly higher at rest and at peak exercise than in the HF group, whose output increased from 3.5 ± 0.4 to 5.6 ± 1.6 L/min. In the RP group, the estimated pump flow increased from 5.3 ± 0.4 to 6.2 ± 0.8, whereas the native cardiac output increased from 0.0 ± 0.5 to 3 ± 1.7 L/min. Cardiac output at peak exercise was inversely correlated with age (r = -0.86, P = 0.001) and mean pulmonary artery pressure (r = -0.75, P = 0.012). Maximal exercise capacity is improved in patients supported by RP as compared to matched HF patients and reaches about 50% of the expected values. Both a spontaneous increase of pump flow at constant pump speed and an increase of the native cardiac output contribute to total flow elevation. These findings may suggest that an automatic pump speed adaptation during exercise would further improve the exercise capacity. This hypothesis should be examined.